1. Field of the Invention
This invention relates to apparatus for feeding strip material intermittently to a press and, more particularly, to apparatus for adjusting the feed lengths of strip material to the press as the feed roll is being driven, to thereby permit adjustments to be made to the feed length while the strip material is being fed.
2. Description of the Prior Art
It is the conventional practice in high speed automatic press operations to feed a strip of stock material from a coil to the dies of the press for punching, stamping, cutting or the like, at a preselected length of the stock material. The stock material must be fed from the coil in timed relation with the press operation so that before the dies contact the stock material, the stock material is moved into a final position by the die pilots as the feed rolls are released from engagement with the stock material. The stock material is then stationarily positioned between the dies. After the press operation is completed, the feed rolls are actuated to advance another length of the stock material to the press. Therefore, the feeding of the stock material to the press must be coordinated with each press operation so that, prior to each operation, a new segment of stock material is in position relative to the dies for the press.
U.S. Pat. Nos. 4,133,216 and 4,138,913 are examples of one type of feeding apparatus for power punch presses in which the feed rolls are drivingly connected by a plurality of meshing gears to an input shaft, which is drivingly connected to the punch press crank shaft. A geared cam drive receives continuous, uniform rotation from the input shaft and converts the rotation to a noncontinuous step-by-step intermittent rotational movement to the driven feed roll. With this arrangement, the feed rolls advance intermittently through a 360.degree. rotational cycle. During the dwell periods of the rotational cycle, the driven feed roll is not rotated and the punching operation is carried out. After the punching operation is completed, the feed rolls are again incrementally advanced so that another preselected length of stock material is passed through the press.
U.S. Pat. Nos. 3,758,011 and 3,784,075 are examples of other types of incremental feed apparatus that convert continuous rotation of a drive shaft to contrarotating oscillating movement of the feed rolls. The drive shaft is connected to a pair of meshing gears, one of which is arranged eccentrically and is connected to a lever that is rotated to-and-fro. Pivotal movement of the lever is transmitted to a shaft that is, in turn, coupled to the feed rolls. The oscillatory movement of the lever and shaft is transmitted to the feed rolls to generate a to-and-fro movement. The feed length can be changed by alternating the amplitude of the oscillatory movement of the feed rolls.
Synchronously with the to-and-fro movement of the feed rolls, the feed rolls move toward one another into a feed position and move away from one another into an idling position. The movement of the feed rolls between the feed and idling positions takes place at the point where the feed rolls change directions of oscillation. A holding mechanism for the work piece is actuated when the feed rolls move from their feed position into their idling position and is deactuated when the rollers move from their idling position into the feed position.
It is also known to make adjustments in the feed lengths of the stock material to the press, as disclosed in U.S. patent application Ser. No. 182,463, now U.S. Pat. No. 4,316,569, where a link member connects an oscillating output shaft to a driven feed roll. The end of the link member adjacent to the output shaft is movable linearly in a direction toward or away from the axis of rotation of the output shaft. The distance of the end of the link member from the axis of rotation of the output shaft determines the degree of movement of the link member and, accordingly, the degree of rotation of the driven feed roll and the feed length of the strip material. A spring biased adjusting member is movable into and out of connection with the end of the link member, so as to selectively move the end of the link member relative to the axis of rotation of the output shaft. Prior to each adjustment in the length, the transmission of rotation to the driven feed roll must be interrupted to permit engagement of the adjusting device to the link member. Once the connection is made and the link member is moved to a selected position, the adjusting device is disconnected and the transmission of rotation to the driven feed roll is again intiated.
While it is known to make adjustments in the feed length, the known devices do not efficiently permit adjustments to be made as rotation is transmitted to the driven feed rolls to provide an instantaneous readout once the adjustment is made of the length of the strips being fed to the press. Therefore, there is need to provide apparatus which permits as in motion adjustment to be made to the feed length as the feed roll intermittently feeds strip material to the press.